As this type of apparatus, there has been suggested an apparatus for suppressing the occurrence of a rattle in accordance with SOC (State of Charge) of a battery (e.g. refer to a patent document 1). According to the apparatus disclosed in the patent document 1, in a case where the rattle occurs, the rattle is supposedly suppressed by reducing engine output and performing the power running drive of a motor generator on a drive side if there is room for the SOC, and by increasing the engine output and performing the regenerative drive of the motor generator on the drive side if there is no room for the SOC.
Incidentally, there has been also suggested an apparatus for controlling the motor generator as a reaction element, so as to depart from a rattle occurrence condition if the input/output toque of a motor is in a rattle occurrence area in a case where an engine start request or stop request is detected (e.g. refer to a patent document 2).